Wood's Lamp Examination

What Is a Wood’s Lamp Examination?

A Wood’s lamp
examination is a procedure that uses transillumination (light) to detect bacterial or fungal skin
infections. It also can detect skin pigment disorders such as vitiligo and other
skin irregularities. This procedure can also be used to determine if you have
a corneal abrasion (scratch)
on the surface of your eye. This test is also known as the black light test or
the ultraviolet light test.

How Does It Work?

A Wood’s lamp is a small handheld device that uses black light to
illuminate areas of your skin. The light is held over an area of skin in a
darkened room. The presence of certain bacteria or fungi, or changes in the
pigmentation of your skin will cause the affected area of your skin to change
color under the light.

Some of the conditions that a Wood’s lamp examination can help
diagnose include:

In the case of scratches on the eye, your doctor will put a
fluorecin solution in your eye, then shine the Wood’s lamp over the affected area.
Abrasions or scratches will glow when the light is on it. There are no risks
associated with the procedure.

What Do I Need to Know About This Test?

Avoid washing the area to be tested before the procedure. Avoid
using makeup, perfume, and deodorant on the area that will be tested. The
ingredients in some of these products can cause your skin to change color under
the light.

The examination will take place in a doctor’s or dermatologist’s
office. The procedure is simple and does not take a long time. The doctor will
ask you to remove clothing from the area that will be examined. The doctor will
then darken the room and hold the Wood’s lamp a few inches away from your skin
to examine it under the light.

What Do the Results Mean?

Normally, the light will look purple or violet and your skin will
not fluoresce (glow) or show any spots under the Wood’s lamp. Your skin will
change color if you have a fungal or bacterial, as some fungi and some bacteria
naturally luminesce under ultraviolet light.

A room that is not dark enough, perfumes, makeup, and skin
products can discolor your skin and cause a "false positive" or "false
negative" result. The Wood’s lamp does not test for all fungal and bacterial
infections. Therefore, you still may have an infection, even if results are
negative.

Your doctor may need to order more laboratory tests or physical
exams before they are able to make a diagnosis.

This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.